Mazda began talking up its plans to launch a new diesel engine to the United States a while back. Mazda wanted to put the diesel engine under the hood of its new Mazda6 in the U.S. during the second half of 2013.

However, it appears Mazda is having a hard time getting the engine certified for use in the United States. Due to delays in certification, the engine has been pushed until late spring of 2014. The company says that it's currently still working on emissions testing for the U.S. market.

Mazda said, "The on-sale date for Mazda6 Skyactiv-D clean-diesel has been moved to late-spring 2014, to accommodate final emissions testing and certification....More information on the Skyactiv-D clean diesel Mazda6 will be available closer to the on-sale date."

Robert Davis, senior vice president of U.S. operations for Mazda said, "I know we had discussed it being in showrooms before the end of the year, and everyone involved in the program is disappointed it will not be, but final certification testing -- the results of which are looking encouraging -- is taking longer than we had initially expected."

Mazda had also hoped the new diesel engine would help further increase its sales in the U.S. Mazda6 sales were up 167% in August compared to August of 2012, but are starting to slow.

"So, I think the same thing of the music industry. They can't say that they're losing money, you know what I'm saying. They just probably don't have the same surplus that they had." -- Wu-Tang Clan founder RZA